Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates to semiconductor lighting systems and more particularly to interior lighting of a vehicle using dimmable assemblies of light emitting diodes.
2. Description of the Related Art
The interior cabins of vehicles, such as automobiles, trains and especially aircraft, currently are illuminated by fluorescent or incandescent lighting systems. The disadvantages of those types of systems include short life of the light emitter or bulb, significant weight, generation of radio frequency interference, heat generation, maintenance costs and fragility.
One solution used to counter the problems identified above has been to use a light emitting diode (LED), either singularly or in groups. U.S. Pat. No. 6,158,882 describes a vehicle lighting system which employs a plurality of LED""s mounted in a linear array to form a lighting strip. Such a strip can be used to wash a wall or ceiling of the vehicle with light. This device is particularly useful to illuminate the cabin of an aircraft. The DC voltage required to illuminate the LED""s is furnished from a power supply hat includes a mechanism for varying the DC voltage to control the intensity of the illumination provided by the lighting strip. Specifically a variable voltage regulator is provided in the system described in the aforementioned patent. This enables the illumination of the vehicle""s interior to be adjusted depending upon the outside light level. For example, in daylight the LED lighting strip typically is driven at a voltage level which provides maximum illumination. At nighttime, that maximum illumination level may interfere with the ability of occupants to see through the vehicle windows. Therefore, a lower interior illumination level is preferred at night.
Electromagnetic interference (EMI), especially in the radio frequency spectrum (RFI) is especially troublesome in aircraft, as such can interfere with navigation and communication systems. Thus variable power supplies often require special filtering and insulating elements to avoid or minimize EMI and RFI. That in turn adds weight and consumes space, both of which are a premium in an aircraft.
Weight always is a major consideration in the construction of aircraft and manufacturers go to great lengths to reduce weight of components where ever possible. Thus it is desirable to reduce the weight of circuits for dimming aircraft cabin lighting.
A lighting assembly for illuminating a vehicle interior has an elongated housing adapted to be mounted in the vehicle interior and has a plurality of electrical terminals for connection to a source of electricity.
A plurality of light emitters, preferably light emitting diodes, is supported by the housing and arranged in a plurality of rows. The light emitters in each row are electrically connected together and to ones of the plurality of electrical terminals wherein application of electricity to selected ones of the plurality of electrical terminals causes illumination of different combinations of the plurality of rows of light emitters. Such selective application of electricity results in the lighting assembly producing different light intensity levels in the vehicle interior.
In the preferred embodiment in which the light emitters are light emitting diodes, each of the rows is divided into groups of light emitting diodes electrically connected in series with the groups for a given row electrically connected in parallel. When the lighting assembly is powered by alternating current, a first set of the groups of light emitting diodes in a given row are connected in an inverse parallel manner to a second set of groups in the given row. Thus each set will illuminate during opposite half-cycles of the alternating current. In another embodiment for use with alternating current, a full-wave rectifier is provided to power the light emitting diodes and the full-wave rectifier may employ some of the light emitting diodes to rectify the alternating current.
In one version of the present lighting system there are first, second and third rows of light emitters with the first and third rows electrically connected in parallel. A switching device is attached to the rows of the lighting assembly. The switching device has a first state in which electricity is applied to only the second row of light emitters, a second state in which electricity is applied to only the first and third rows of light emitters, and a third state in which electricity is applied to every row of light emitters.